Stepwise N–H bond formation from N<sub>2</sub>-derived iron nitride, imide and amide intermediates to ammonia

MacLeod, K. Cory; McWilliams, Sean F.; Mercado, Brandon Q.; Holland, Patrick L.

doi:10.1039/c6sc00423g

Cited by 80 publications

(85 citation statements)

References 69 publications

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“…[24] TheM çssbauer spectrum of 4 has an isomer shift of 0.91 mm s À1 (Figure S25), which is comparable to that for known high-spin iron(II) complexes in tetrahedral environments, [24,25] and is in excellent agreement with the DFTcomputed isomer shift of 0.95 mm s À1 .T he solution magnetic moment of 4 (m eff = 6.1(1) BM) is within error of the expected spin-only magnetic moment for uncoupled high-spin Fe 2+ and Co 2+ metal centers. TheCo ÀObond lengths in 4 are approximately 0.02 longer than in 3 while the FeÀOb onds are about 0.03 shorter than in the previously reported [L Me 3 Fe(m-OH)] 2 complex.…”

Section: Zuschriftenmentioning

confidence: 99%

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate

et al. 2017

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The characterization of intermediates formed through the reaction of transition-metal complexes with dioxygen (O ) is important for understanding oxidation in biological and synthetic processes. Here, the reaction of the diketiminate-supported cobalt(I) complex L Co with O gives a rare example of a side-on dioxygen complex of cobalt. Structural, spectroscopic, and computational data are most consistent with its assignment as a cobalt(III)-peroxo complex. Treatment of L Co(O ) with low-valent Fe and Co diketiminate complexes affords isolable oxo species with M O "diamond" cores, including the first example of a crystallographically characterized heterobimetallic bis(μ-oxo) complex of two transition metals. The bimetallic species are capable of cleaving C-H bonds in the supporting ligands, and kinetic studies show that the Fe/Co heterobimetallic species activates C-H bonds much more rapidly than the Co/Co homobimetallic analogue. Thus heterobimetallic oxo intermediates provide a promising route for enhancing the rates of oxidation reactions.

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Section: Zuschriftenmentioning

confidence: 99%

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate

et al. 2017

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“…[5,6] For both pathways, efficient charge storage and transfer to N 2 define key challenges, particularly for the development of electrocatalytic methods. [7,8] Proton-coupled electron transfer [9,10] and storage of reduction equivalents within M À H bonds were recently highlighted approaches. [11,12] However, general guidelines that evolve from electronic structure considerations of key intermediates are yet to be developed.…”

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confidence: 99%

Dinitrogen Splitting Coupled to Protonation

et al. 2017

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The coupling of electron- and proton-transfer steps provides a general concept to control the driving force of redox reactions. N splitting of a molybdenum dinitrogen complex into nitrides coupled to a reaction with Brønsted acid is reported. Remarkably, our spectroscopic, kinetic, and computational mechanistic analysis attributes N-N bond cleavage to protonation in the periphery of an amide pincer ligands rather than the {Mo-N -Mo} core. The strong effect on electronic structure and ultimately the thermochemistry and kinetic barrier of N-N bond cleavage is an unusual case of a proton-coupled metal-to-ligand charge transfer process, highlighting the use of proton-responsive ligands for nitrogen fixation.

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“…33 The iron(II) hydride dimer of the L Me3 ligand system also has a significant advantage in that it can be synthesized easily by treatment of the iron(II) chloride complex with cyclohexylmagnesium chloride. 33, 34 …”

Section: Resultsmentioning

confidence: 99%

“…The hydride complexes [L Me,iPr FeH] 2 ( 1 ) and [L Me3 FeH] 2 ( 4 ) were prepared according to published procedures. 33, 34, 50 The deuteride analogue [L Me3 FeD] 2 ( 4-D ) was prepared by exposing 4 to 1 atm of D 2 for 2 minutes, removing the headspace, and repeating this sequence three times.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and Mechanism of Formation of Hydride–Sulfide Complexes of Iron

et al. 2017

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Iron-sulfide complexes with hydride ligands provide an experimental precedent for spectroscopically detected hydride species on the iron-sulfur FeMoco of nitrogenase. In this contribution, we expand upon our recent synthesis of the first iron sulfide hydride complex from an iron hydride and a sodium thiolate (Arnet, N. A.; Dugan, T. R.; Menges, F. S.; Mercado, B. Q.; Brennessel, W. W.; Bill, E.; Johnson, M. A.; Holland, P. L., J. Am. Chem. Soc. 2015, 137, 13220–13223). First, we describe the isolation of an analogous iron sulfide hydride with a smaller diketiminate supporting ligand, which benefits from easier preparation of the hydride precursor and easier isolation of the product. Second, we describe mechanistic studies on the C-S bond cleavage through which the iron sulfide hydride product is formed. In a key experiment, use of cyclopropylmethanethiolate as the sulfur precursor leads to products from cyclopropane ring opening, implicating an alkyl radical as an intermediate. Combined with the results of isotopic labeling studies, the data are consistent with a mechanism in which homolytic C-S bond cleavage is followed by rebound of the alkyl radical to abstract a hydrogen atom from the iron to give the observed alkane and iron-sulfide products.

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Stepwise N–H bond formation from N₂-derived iron nitride, imide and amide intermediates to ammonia

Abstract: The pathway from N2 to NH3 at low-coordinate iron complexes is shown through crystallographic and spectroscopic characterization of intermediates, including bridging nitride, imide, and amides. Proton-coupled electron transfer plays a key role in the transformations.

Cited by 80 publications

References 69 publications

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate

Dinitrogen Splitting Coupled to Protonation

Synthesis and Mechanism of Formation of Hydride–Sulfide Complexes of Iron

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Stepwise N–H bond formation from N2-derived iron nitride, imide and amide intermediates to ammonia

Abstract: The pathway from N2 to NH3 at low-coordinate iron complexes is shown through crystallographic and spectroscopic characterization of intermediates, including bridging nitride, imide, and amides. Proton-coupled electron transfer plays a key role in the transformations.

Cited by 80 publications

References 69 publications

Enhancement of C−H Oxidizing Ability in Co–O2 Complexes through an Isolated Heterobimetallic Oxo Intermediate

Enhancement of C−H Oxidizing Ability in Co–O2 Complexes through an Isolated Heterobimetallic Oxo Intermediate

Dinitrogen Splitting Coupled to Protonation

Synthesis and Mechanism of Formation of Hydride–Sulfide Complexes of Iron

Contact Info

Product

Resources

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Stepwise N–H bond formation from N₂-derived iron nitride, imide and amide intermediates to ammonia

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate

Enhancement of C−H Oxidizing Ability in Co–O₂ Complexes through an Isolated Heterobimetallic Oxo Intermediate